core: add NMRefString

NMRefString is a simple, refcounted, immutable string. Increasing/decreasing
the refcount does not affect const-ness.

It can be used just like a regular 'const char *' pointer. The only
difference is that you need special alloc/free functions.

3 files changed, 182 insertions, 0 deletions

diff --git a/src/NetworkManagerUtils.c b/src/NetworkManagerUtils.c
index fdaa31cd77..7757643b29 100644
--- a/src/NetworkManagerUtils.c
+++ b/src/NetworkManagerUtils.c
@@ -2713,3 +2713,127 @@ nm_utils_setpgid (gpointer unused G_GNUC_UNUSED)
 	pid = getpid ();
 	setpgid (pid, pid);
 }
+
+/******************************************************************
+ * NMRefString
+ ******************************************************************/
+
+#ifdef NM_MORE_ASSERTS
+#define NM_STRING_CANARY(s) (GPOINTER_TO_UINT (s) ^ ((guint) 30112031329))
+#endif
+
+typedef struct _NMString {
+#ifdef NM_STRING_CANARY
+	guint _canary;
+#endif
+	int ref_count;
+	char str[1];
+} _NMString;
+
+static inline _NMString *
+_nm_ref_string_up_cast (NMRefString nmstr)
+{
+	_NMString *s;
+
+	s = (_NMString *) (((char *) nmstr) - G_STRUCT_OFFSET (_NMString, str));
+#ifdef NM_STRING_CANARY
+	g_return_val_if_fail (s->_canary == NM_STRING_CANARY (s), NULL);
+#endif
+	g_return_val_if_fail (s->ref_count > 0, NULL);
+
+	nm_assert (s->str == nmstr);
+
+	return s;
+}
+
+NMRefString
+nm_ref_string_new (const char *str)
+{
+	_NMString *s;
+	gsize len;
+
+	if (!str)
+		return NULL;
+
+	len = strlen (str) + 1;
+
+	s = g_malloc (G_STRUCT_OFFSET (_NMString, str) + len);
+	s->ref_count = 1;
+#ifdef NM_STRING_CANARY
+	s->_canary = NM_STRING_CANARY (s);
+#endif
+	memcpy (s->str, str, len);
+	return s->str;
+}
+
+NMRefString
+nm_ref_string_ref (NMRefString nmstr)
+{
+	_NMString *s;
+
+	if (!nmstr)
+		return NULL;
+
+	s = _nm_ref_string_up_cast (nmstr);
+	g_return_val_if_fail (s, NULL);
+
+	s->ref_count++;
+	return s->str;
+}
+
+void
+nm_ref_string_unref (NMRefString nmstr)
+{
+	_NMString *s;
+
+	if (!nmstr)
+		return;
+
+	s = _nm_ref_string_up_cast (nmstr);
+	g_return_if_fail (s);
+
+	if (--s->ref_count <= 0) {
+#ifdef NM_STRING_CANARY
+		s->_canary = 0;
+#endif
+		g_free (s);
+	}
+}
+
+NMRefString
+nm_ref_string_replace (NMRefString nmstr, const char *str)
+{
+	_NMString *s, *s2;
+	gsize len;
+
+	if (!nmstr)
+		return nm_ref_string_new (str);
+	if (!str) {
+		nm_ref_string_unref (nmstr);
+		return NULL;
+	}
+
+	s = _nm_ref_string_up_cast (nmstr);
+	g_return_val_if_fail (s, NULL);
+
+	if (strcmp (s->str, str) == 0)
+		return nmstr;
+
+	if (s->ref_count == 1) {
+		len = strlen (str) + 1;
+
+		s2 = g_realloc (s, G_STRUCT_OFFSET (_NMString, str) + len);
+
+#ifdef NM_STRING_CANARY
+		s2->_canary = NM_STRING_CANARY (s2);
+#endif
+		memcpy (s2->str, str, len);
+		return s2->str;
+	} else {
+		s->ref_count--;
+		return nm_ref_string_new (str);
+	}
+}
+
+/******************************************************************/
+
diff --git a/src/NetworkManagerUtils.h b/src/NetworkManagerUtils.h
index 7624715264..c0ce323781 100644
--- a/src/NetworkManagerUtils.h
+++ b/src/NetworkManagerUtils.h
@@ -201,4 +201,10 @@ gboolean nm_utils_get_testing_initialized (void);
 NMUtilsTestFlags nm_utils_get_testing (void);
 void _nm_utils_set_testing (NMUtilsTestFlags flags);
 
+typedef const char *NMRefString;
+NMRefString nm_ref_string_new (const char *str);
+NMRefString nm_ref_string_ref (NMRefString nmstr);
+void nm_ref_string_unref (NMRefString nmstr);
+NMRefString nm_ref_string_replace (NMRefString nmstr, const char *str);
+
 #endif /* __NETWORKMANAGER_UTILS_H__ */
diff --git a/src/tests/test-general-with-expect.c b/src/tests/test-general-with-expect.c
index 9491801d42..300ed2145d 100644
--- a/src/tests/test-general-with-expect.c
+++ b/src/tests/test-general-with-expect.c
@@ -35,6 +35,57 @@
 /*******************************************/
 
 static void
+test_nm_ref_string (void)
+{
+	const char *nm_str, *s1, *s2;
+
+	nm_str = nm_ref_string_new ("hallo");
+
+	g_assert_cmpstr (nm_str, ==, "hallo");
+
+	nm_ref_string_ref (nm_str);
+	g_assert_cmpstr (nm_str, ==, "hallo");
+
+	nm_ref_string_unref (nm_str);
+	g_assert_cmpstr (nm_str, ==, "hallo");
+
+	nm_str = nm_ref_string_replace (nm_str, "hallo");
+	g_assert_cmpstr (nm_str, ==, "hallo");
+
+	nm_str = nm_ref_string_replace (nm_str, "hallo2");
+	g_assert_cmpstr (nm_str, ==, "hallo2");
+
+	nm_ref_string_unref (nm_str);
+
+	/* replace() reallocs old memory if ref-count is 1. */
+	s1 = nm_ref_string_new ("abcdef");
+	g_assert_cmpstr (s1, ==, "abcdef");
+	s2 = nm_ref_string_replace (s1, "ABC");
+	g_assert_cmpstr (s2, ==, "ABC");
+	nm_ref_string_unref (s2);
+
+	/* replace() reallocs old memory if ref-count is 1. */
+	s1 = nm_ref_string_new ("ABC");
+	g_assert_cmpstr (s1, ==, "ABC");
+	s2 = nm_ref_string_replace (s1, "abcdef");
+	g_assert_cmpstr (s2, ==, "abcdef");
+	nm_ref_string_unref (s2);
+
+	/* replace allocates new memory if ref-count larger 1. */
+	s1 = nm_ref_string_new ("ABC");
+	g_assert_cmpstr (s1, ==, "ABC");
+	nm_ref_string_ref (s1);
+	s2 = nm_ref_string_replace (s1, "abcdef");
+	g_assert_cmpstr (s2, ==, "abcdef");
+	g_assert_cmpstr (s1, ==, "ABC");
+	g_assert (s1 != s2);
+	nm_ref_string_unref (s2);
+	nm_ref_string_unref (s1);
+}
+
+/*******************************************/
+
+static void
 test_nm_utils_monotonic_timestamp_as_boottime (void)
 {
 	gint64 timestamp_ns_per_tick, now, now_boottime, now_boottime_2, now_boottime_3;
@@ -501,6 +552,7 @@ main (int argc, char **argv)
 {
 	nmtst_init_assert_logging (&argc, &argv, "DEBUG", "DEFAULT");
 
+	g_test_add_func ("/general/nm_ref_string", test_nm_ref_string);
 	g_test_add_func ("/general/nm_utils_monotonic_timestamp_as_boottime", test_nm_utils_monotonic_timestamp_as_boottime);
 	g_test_add_func ("/general/nm_utils_kill_child", test_nm_utils_kill_child);
 	g_test_add_func ("/general/nm_utils_array_remove_at_indexes", test_nm_utils_array_remove_at_indexes);